Illegal instruction in GHC 6.5 generated code.

[Simon Marlow]

On 23 June 2006 17:43, Caio Marcelo wrote:

> On 6/23/06, Simon Marlow <simonmarhaskell at gmail.com> wrote:
>> What did I do wrong?
> 
> Did you changed the Judy/Map.hs code to not use Dummy (see below)? The
> code I commited is the version with the workaround.
> 
> Anyway, I'm going to darcs pull and recompile GHC to check if the
> behaviour changes.
> 
> -----------8<------------
> Index: Judy/Map.hs
> ===================================================================
> --- Judy/Map.hs (revisão 10752)
> +++ Judy/Map.hs (cópia de trabalho)
> @@ -56,7 +56,8 @@
>  class Dummy a
>  instance Dummy a
> 
> -instance Dummy a => Refeable a where
> +--instance Dummy a => Refeable a where
> +instance Refeable a where
>      toRef a = do
>          a' <- newStablePtr a
>          return (ptrToWordPtr (castStablePtrToPtr a'))
> ---------->8-------------

Ok, I reproduced it.  I think this may be a bug in your code, but I'm not completely sure.

Compiling the program with -debug turns the crash into an assertion failure.  Furthermore, running the program with +RTS -DS, which causes all free memory to be filled with 0xaaaaaaaa, turns the crash into this:

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 47963533074768 (LWP 15726)]
0x0000003fa1e75b30 in memcpy () from /lib64/libc.so.6
(gdb) where
#0  0x0000003fa1e75b30 in memcpy () from /lib64/libc.so.6
#1  0x000000000045329e in JudyHSIterFirst (PArray=0x0, PPIter=Variable "PPIter" is not available.
) at JudyHS.c:983
#2  0x000000000040e2b1 in s2KX_info ()
#3  0x000000000066fb90 in ?? ()
#4  0x00002b9f616828d0 in ?? ()
#5  0x0000000000000000 in ?? ()

which looks suspicious.  Delving a little further:

(gdb) up
#1  0x000000000045329e in JudyHSIterFirst (PArray=0x0, PPIter=Variable "PPIter" is not available.
) at JudyHS.c:983
983                 memcpy(PIter->hsi_String, String, Length);
(gdb) p *PIter
$1 = {hsi_Alloc = 32, hsi_MaxLength = 0, hsi_Length = 12297829382473034410, 
  hsi_Hash = 0, hsi_String = "\000\000\000\000\000\000\000"}
(gdb) p String
$2 = (uint8_t *) 0xaaaaaaaaaaaaaaaa <Address 0xaaaaaaaaaaaaaaaa out of bounds>
(gdb) p Length
$3 = 12297829382473034410

So it looks like you're passing some free memory to a foreign function, perhaps.  Is this any help?

Cheers,
	Simon